media: Cleanup class/struct forward declarations

media/blink/texttrack_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BLINK_TEXTTRACK_IMPL_H_
 #define MEDIA_BLINK_TEXTTRACK_IMPL_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "media/base/text_track.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace blink {
-class WebInbandTextTrackClient;
 class WebMediaPlayerClient;
 }
 
 namespace media {
 
 class WebInbandTextTrackImpl;
 
 class TextTrackImpl : public TextTrack {
  public:
   // Constructor assumes ownership of the |text_track| object.
@@ skipping 22 matching lines @@
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   blink::WebMediaPlayerClient* client_;
   std::unique_ptr<WebInbandTextTrackImpl> text_track_;
   DISALLOW_COPY_AND_ASSIGN(TextTrackImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_TEXTTRACK_IMPL_H_